NIOSH Publication No. 2005-151:

NIOSH Pocket Guide to Chemical Hazards

September 2005

Sulfur dioxide

CAS
7446-09-5

SO2

RTECS
WS4550000
Synonyms & Trade Names

Sulfurous acid anhydride, Sulfurous oxide, Sulfur oxide
DOT ID & Guide
1079 / 125

Exposure
Limits

NIOSH REL: TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3)
OSHA PEL: TWA 5 ppm (13 mg/m3)
IDLH
100 ppm See: 7446095
Conversion
1 ppm = 2.62 mg/m3
Physical Description
Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14°F. Shipped as a liquefied compressed gas.]
MW: 64.1
BP: 14°F
FRZ: -104°F
Sol: 10%
VP: 3.2 atm
IP: 12.30 eV
RGasD: 2.26

Fl.P: NA
UEL: NA
LEL: NA

Nonflammable Gas
Incompatibilities & Reactivities

Powdered alkali metals (such as sodium & potassium), water, ammonia, zinc, aluminum, brass, copper [Note: Reacts with water to form sulfurous acid (H2SO3).]
Measurement Methods
NIOSH 3800, 6004; OSHA ID104, ID200
See: NMAM or OSHA Methods
Personal Protection & Sanitation
(See protection)
Skin: Frostbite
Eyes: Frostbite
Wash skin: No recommendation
Remove: When wet or contaminated (liquid)
Change: No recommendation
Provide: Frostbite wash
First Aid
(See procedures)
Eye: Frostbite
Skin: Frostbite
Breathing: Respiratory support

Respirator Recommendations
NIOSH
Up to 20 ppm:
(APF = 10) Any chemical cartridge respirator with cartridge(s) providing protection against the compound of concern*
(APF = 10) Any supplied-air respirator*
Up to 50 ppm:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode*
(APF = 25) Any powered, air-purifying respirator with cartridge(s) providing protection against the compound of concern*
Up to 100 ppm:
(APF = 50) Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern
(APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and cartridge(s) providing protection against the compound of concern*
(APF = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode*
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece
Emergency or planned entry into unknown concentrations or IDLH conditions:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
Escape:
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern/Any appropriate escape-type, self-contained breathing apparatus
Important additional information about respirator selection
Exposure Routes
inhalation, skin and/or eye contact
Symptoms
Irritation eyes, nose, throat; rhinorrhea (discharge of thin mucus); choking, cough; reflex bronchoconstriction; liquid: frostbite
Target Organs
Eyes, skin, respiratory system
See also: INTRODUCTION   See ICSC CARD: 0074   See MEDICAL TESTS: 0215